A species listed 'Historic' in Massachusetts may be present in Savery Pond:
Lemna valdiviana (Valdivia or pale duckweed).

Gradations of rarity used by NHESP in Massachusetts: Historic─Endangered─Threatened─Special Concern─Watch-Listed.
The latter category is assigned to plants whose distribution in the state is not yet sufficiently known and
that may prove to be rare upon accumulating data.